1. Field of the Invention
The present invention relates to an IC package in which signal transfer elements, such as pads or connecting terminals or the like (hereinafter referred to as pins) are disposed on a plurality of faces of a polyhedron, and more particularly to a polyhedral IC package which is designed with consideration given to a device that is suited for three-dimensional mounting.
2. Description of Related Art
FIG. 10(A) and 10(B) is a perspective view which shows an IC package of the past.
An IC package is generally the means of implementing an IC that requires a large number of pins, and in which the pins are arranged in a matrix pattern as shown in the drawing.
This example is one which shows the construction of an IC package that is used with a multi-layer printed circuit board in the past, FIG. 10 (A) showing the solder side, from which the pins 302 are clearly visible, and FIG. 10 (B) showing the front, component side, from which the pins 302 are barely visible.
As shown in FIG. 10 (A) and FIG. 10 (B), the pins 302 are mounted on only one side.
FIG. 11 is a drawing which shows the internal construction of the above-noted example.
The internal construction is this example is one formed by a semiconductor 303, the conductive leads 304, and the bonding wires 305, which make connections between the semiconductor 303 and the conductive leads 304.
As shown in this drawing, because the pins 302 are arranged on one base surface, in order to increase the number of pins, it is necessary either to reduce the spacing between pins, or to make the IC package itself larger.
However, the pin spacing is limited by considerations of mounting accuracy and of electrical characteristics, and enlargement of the IC package is also limited, because of the effect of conductive lead extension on electrical characteristics and the need to achieve mounting density.
Additionally, while the Japanese Unexamined Patent Publications Nos. 61-99361 and 7-86493 describe a method of wiring a plurality of semiconductor chips arranged almost in a straight line on a plan and on a face of a polyhedron, this method is one of shortening the wiring length between a plurality of semiconductor chips which are mounted within an IC package, rather than one which would provide a direct solution to the problem of wiring between IC packages.
In the case in which an IC package is mounted three-dimensionally, with the exception of an IC that is mounted on an outer surface, because access from the outside becomes impossible, it is impossible to mount an interface such as an interface for light, for fluid, or for gas.
Additionally, cooling and maintenance of an IC package located in a deep part becomes extremely difficult.
In the above-described prior art, because pins were only mounted on one surface of a three-dimensional IC package, with improvement in the functionality of ICs, the number of pins required on an IC package increases, and the resulting increase in the number of pins is accompanied by the problem of a narrowing of the pin-to-pin spacing.
To establish spacing between pins, as the demand for an increase in the number of IC package pins increases, because the distance between the semiconductor chip and the IC package pins increases, the wiring length between the semiconductor chip inside the IC package and the outside of the IC package becomes long, this presenting the problem of a worsening of the electrical characteristics.
Additionally, because the electrical interface between IC packages is implemented by transmission via the pattern on a printed circuit board, the transmission paths become long, and the wiring length between IC packages becomes long, this leading to the problem of a worsening of the electrical characteristics.
Additionally, if IC packages are mounted three-dimensionally, with the exception of an IC package which is located on an outer surface, because access from the outside is impossible, when IC packages are mounted three-dimensionally, with the exception of an IC package that is located on an outer surface, it is not possible to mount an interface such as an interface, for light, fluid, or gas, or other non-electrical interface.
When mounting IC packages to a multi-layer printed circuit board, there are cases in which the circuit configuration of the printed circuit board makes it difficult to make electrical contact with the terminals on the surface for adhesion to the substrate, and in inspection after mounting, there are cases in which it is difficult to make electrical contact with a terminal near an IC package terminal for the purpose of measuring the electrical characteristics.
Additionally, because of circuit configuration and electrical characteristics considerations, there is a need to mount components and wiring with high density in the region of an IC package, and also in order to mount components which require a physical mounting spacing on one and the same board, circuitry becomes concentrated only in the region of an IC package, resulting in a localized high circuit density.
To accommodate this, a problem arises in that the entire board must be made multi-layer.
In view of the above-described drawbacks in the prior art, an object of the present invention is to provide polyhedral IC package which enables an increase in the number of pins without making the spacing between pins narrow.
Another object of the present invention is to provide a polyhedral IC package which shortens the distance between a semiconductor chip that is mounted in the IC package and the pins thereof.
Yet another object of the present invention is to provide a polyhedral IC package that facilitates three-dimensional mounting.
Yet another object of the present invention is to provide a polyhedral IC package that, when mounting three-dimensionally, enables access from the outside to an IC package, even if the package is not located on an outer surface.
Yet another object of the present invention is to provide a polyhedral IC package which, after mounting, enables the measurement of electrical characteristics in the region of a terminal.
Still another object of the present invention is to provide a polyhedral IC package which, by mounting a plurality of the IC packages onto a printed circuit board, enables the achievement of a high-density printed circuit board with a small amount of partially high-concentration regions.